Recent Harvard graduates Frederick O. Vaille, and Henry R. Walcott, went to Denver and met a saloonkeeper, Sam Morgan and together secured 161 customers, enough to warrant a return to Boston to secure a new telephone franchise from the American Bell Telephone Company.

When the franchise was secured, wires were strung, boys were hired as operators, a switchboard was installed and the Denver Telephone Dispatch Company opened for business on February 24, 1879. The Denver exchange was the seventeenth in the nation, opening just nine days after the Minneapolis exchange. Denver's Rocky Mountain News reported that "The Telephone Company are adding new subscribers to the system every day."[citation needed]

The competitive battle raged as the Dispatch Company acquired better transmitters and added Golden, Black Hawk, Georgetown and Central City to their calling area. When the American Bell Company won their patent infringement suit with Western Union, the Bell companies absorbed the Western Union companies. In Denver, competition for local service was absent from the market until 1997.

In 1880, Vaille sold two of his four franchise contracts back to American Bell, who sold them to Horace Tabor in Leadville. In January 1881, Vaille joined a group of Denver business leaders to form the Colorado Telephone Company. Denver Dispatch faded into history when Vaille sold his remaining two Bell contracts to the Colorado Telephone Company. Henry Wolcott was the president of Colorado Telephone, while Vaille stayed on as general manager for three years.

Meanwhile, the Colorado Telephone Company began to grow, as "boomer linemen" strung wire to ranches and farm towns in the flat lands, and to mines and mining towns in the mountains, and along Colorado's front range. Colorado Telephone purchased the Leadville company in 1888.

The Denver Dispatch Company was less than two years old when the Rocky Mountain Telephone Company began in Salt Lake City, Utah with less than 100 subscribers. With the financial backing of American Bell, The Rocky Mountain Bell Telephone Company replaced Rocky Mountain Telephone in 1883. Rocky Mountain Bell immediately began an aggressive campaign to buy nearly every small telephone company in the region, and their operating territory soon covered nearly all of Utah, Montana, Idaho, and Wyoming.

A combination of overspending, careless management, and the logistical difficulties of covering an extremely large, sparsely populated territory would eventually put Rocky Mountain Bell in financial trouble.[vague]

These business practices stopped in 1911 when Colorado Telephone, Tri-State Telephone, and Rocky Mountain Bell merged to form The Mountain States Telephone and Telegraph Company. Vaille was well aware of Rocky Mountain Bell's problems and he insisted that Colorado Telephone Company managers take over the majority of management positions in the former Rocky Mountain Bell Company territory. Vaille served as a Mountain States director until his death in 1920.

MST&T commonly did business as Mountain States Telephone until 1969, when the new Bell System logo came into use and the company name was colloquially referred to as Mountain Bell. The company provided telephone services in Colorado, Utah, Arizona, New Mexico, Montana, Southern Idaho, Wyoming, and the El Paso, Texas vicinity. Additionally, MST&T acquired controlling interest in the Malheur Home Telephone Company in Oregon, better known as Malheur Bell. MST&T operated Malheur Bell as a wholly owned independent subsidiary, an arrangement that continued until 2009.

Usage of the Mountain Bell name has recently been reactivated by Unical Enterprises, who began producing telephones under the Mountain Bell name in 2006. Additionally, the MountainBell.com domain is still active and rolls over to the CenturyLink webpage.

From 1929 to 1984 the Mountain Bell headquarters was located at 931 14th Street in Denver, Colorado. As part of a company wide real estate savings effort, areas of the building interior was remodeled in 2009 and 2010, along with the adjoining 930 building to accommodate employees vacating leased space in the Qwest headquarters building at 1801 California St.

Northwestern Bell was formerly the Iowa Telephone Company, which changed its name to Northwestern Bell in 1920. It then absorbed the operations of companies such as the Northwestern Telephone Exchange, the Tri-State Telephone Company, Dakota Central Telephone Company, and the Nebraska Telephone Company.

The Northwestern Bell headquarters was located at 1314 (DOTM) Douglas Street in Omaha, Nebraska. It remained incorporated in Iowa, however.

In 1988, U S WEST became the first Baby Bell to have its different Bell Operating Companies carry on business under a single name. U S WEST Communications became a "d/b/a" name for Mountain Bell as well as Northwestern Bell and Pacific Northwest Bell; however, the three companies remained legally separate. The three companies also began using the U S WEST Communications logo, which continued to include the Bell symbol.

On January 1, 1991, U S WEST merged its three operating companies. As part of the deal, Northwestern Bell and Pacific Bell were folded into Mountain Bell[4][5] Mountain States Telephone and Telegraph, the surviving company, changed its name to U S WEST Communications, Inc. on January 2, 1991.

U S WEST Communications was the first local telephone company to offer Caller ID service in 1991, nearly four years before any other local telco could do so. They were the first US telco to upgrade their PSTN to electronic switching before 1990 and they were the first to offer residential and business ISDN and later, DSL services to their customers by 1997.

U S WEST, since 1984, had been selling telephone equipment under the Northwestern Bell name. In 1992, U S WEST granted Unical Enterprises, who had been producing phones under the "La Phone" brand, the right to become the exclusive licensee to produce telephones under the Northwestern Bell name, which are still produced under the BELL Phones by Northwestern Bell Phones brand.[citation needed]

In 1999, U S WEST announced plans to sell 530,000 access lines in largely rural areas to the independent company Citizens Communications for $1.65 billion.[8] The sale would not have included U S WEST Dex directories in those territories. The transaction remained incompleted before 2000.

In 2000, Qwest Communications International acquired U S WEST in a hostile takeover. At the time, U S WEST was trying to acquire Global Crossing, and resisted Qwest's takeover. Qwest was a much smaller company in terms of employees and market capitalization when it obtained control of the Regional Bell Operating Company. Because U S WEST's stock was trading at very high prices during the dot-com bubble, Qwest was able to purchase the larger firm, and the Bell Operating Company was renamed Qwest Corporation.[9]

In 2001, Qwest, which acquired U S WEST in 2000, terminated the sale of rural telephone lines agreed upon in 1999 because Citizens refused to complete the transaction.[10]

On December 14, 2009, Qwest Corporation absorbed the operations of its long-time subsidiary Malheur Bell.[11]

On April 1, 2011, CenturyLink completed its acquisition of Qwest. At that point, Qwest Corporation became a subsidiary of CenturyLink and began doing business as CenturyLink QC effective August 8, 2011. The merger represents a reunion of exchanges acquired by Pacific Telecom in the 1990s that had been separated from U S WEST Communications.

Since acquisition by CenturyLink, Qwest Corporation has issued bonds traded on the New York Stock Exchange under the CTQ and CTW tickers.